1. Field of the Invention
The present invention relates to a vehicle headlamp, and more particularly, to a structure of the portion of a vehicle headlamp where a light-source bulb is fixed to a reflector.
2. Prior Art
In a vehicle headlamp, a light-source bulb is generally fixed to a reflector by a bulb fixing member as shown in FIG. 7.
In this vehicle headlamp, a light-source bulb 2 has a flange portion 2d formed on the peripheral surface of a bulb supporting portion 2c that supports a bulb body 2b. A reflector 4 has a bulb insertion hole 4b in the reflector body 4A so that the bulb insertion hole 4b receives the bulb body 2b of the light-source bulb 2. The reflector 4 has also an annular wall 4B in the reflector body 4A. The annular wall 4B protrudes rearward from the periphery of the bulb insertion hole 4b. 
The bulb supporting portion 2c of the light-source bulb 2 is slid and fitted on the inner peripheral surface of the annular wall 4B of the reflector 4 so that the flange portion 2d abuts on the rear end face of the annular wall 4B. Then, a bulb fixing member 6 is fitted on the rear end of the annular wall 4B so that the front and rear sides of the flange portion 2d of the bulb 2 are sandwiched and held between the annular wall 4B and the bulb fixing member 6. The light-source bulb 2 is thus fixed to the reflector 4.
However, such a lamp fixture that has the bulb supporting portion 2c which is slid and fitted on the inner peripheral surface of the annular wall 4B of the reflector 4 has problems. The bulb supporting portion 2c of the light-source bulb 2 completely closes the bulb insertion hole 4b of the reflector 4. Therefore, the heat, which is radiated together with light from the filament 2a of the light-source bulb 2 when the light-source bulb 2 is turned-on, is confined inside the inner space of the reflector 4.
This causes the temperature rise in the reflector 4. When the reflector 4 is made of resins, a thermal deformation can easily occur in the reflector 4.
Generally, a structure in which the bulb supporting portion 2c of the light-source bulb 2 is slid and fitted on the inner peripheral surface of the annular wall 4B of the reflector 4 is often employed when the bulb supporting portion 2c of the light-source bulb 2 is molded with resins. In such a case, however, a thermal deformation can easily occur in the bulb supporting portion 2c or in the O-ring 8 mounted on the bulb supporting portion 2c for use in the sliding and fitting operation.
Accordingly, the present invention is to solve the above problems with the prior art lamp structure.
It is an object of the present invention to provide a vehicle headlamp capable of preventing a temperature rise in a reflector and thus reducing the thermal deformation of the reflector, etc.
The present invention accomplishes the above object by improving the structure of the annular wall of a reflector.
More specifically, the above object is accomplished by a unique structure of the present invention for a vehicle headlamp that includes:
a light-source bulb,
a reflector for reflecting light from the light-source bulb in a forward direction, and
a bulb fixing member for fixing the light-source bulb to the reflector; wherein
the light-source bulb is comprised of a bulb body, a bulb supporting portion for supporting the bulb body, and a flange portion formed on the peripheral surface of the bulb supporting portion,
the reflector includes a reflector body having a bulb insertion hole for inserting the bulb body therein and an annular wall protruding rearward from the periphery of the bulb insertion hole of the reflector body, and
the light-source bulb is fixed to the reflector by sliding and fitting the bulb supporting portion of the light-source bulb on an inner peripheral surface of the annular wall so that the flange portion abuts on the rear end of the annular wall, and then holding the front and rear sides of the flange portion by the annular wall and the bulb fixing member; and
in the present invention:
the annular wall is provided with at least one notch hole that extends through the annular wall, and such a notch hole is located at a position ahead of where the bulb supporting portion is fitted in the annular wall.
In this headlamp of the present invention, the xe2x80x9cbulb fixing memberxe2x80x9d is not specifically limited in terms of the structure as long as the bulb fixing member serves to fix the light-source bulb to the reflector by holding, together with the annular wall, both front and rear sides of the flange portion of the light-source bulb.
Also, it should be noted that a part of the xe2x80x9cbulb supporting portionxe2x80x9d of the bulb that is slid and fitted on the inner peripheral surface of the annular wall of the reflector may be the outer peripheral surface of the bulb supporting portion itself. However, that part of the bulb supporting portion may be another member such as an O-ring mounted on the bulb supporting portion.
Furthermore, the xe2x80x9cnotch holexe2x80x9d is not specifically limited in terms of the structure including shape, size, position and number as long as it extends through the annular wall of the reflector and is formed at a position located ahead (or on the front side) of the position where the bulb supporting portion is fitted in the annular wall.
The present invention is for a vehicle headlamp of the type in which the light-source bulb is fixed to a reflector in such a manner that the bulb supporting portion of the light-source bulb is slid and fitted on the inner peripheral surface of the annular wall of the reflector, thus letting the flange portion abut on the rear end face of the annular wall; and then both front and rear sides of the flange portion are sandwiched by the end surface of the annular wall and the bulb fixing member. However, in this type of lamp fixtures, the bulb supporting portion of the light-source bulb completely closes the bulb insertion hole of the reflector. As a result, the heat radiated from the light-source bulb is confined within the inner space of the reflector.
In the vehicle headlamp of the present embodiment, however, at least one notch hole that extends through the annular wall is formed so as to be located ahead (or on the front side) of the position where the bulb supporting portion of the light-source bulb is fitted in the annular wall. Thus, the notch hole allows the inner space of the reflector to communicate with the outer space of the reflector, so that the heat in the inner space of the reflector is dissipated to the outside of the reflector through the notch hole.
Accordingly, in the headlamp of the present invention, the reflector is prevented from being heated to a high temperature. Even when the reflector is made of a resin material, it is less susceptible to a thermal deformation. Moreover, even when the bulb supporting portion of the light-source bulb is made of resins, the element such as the bulb supporting portion, the O-ring mounted thereto for the sliding and fitting operation are prevented from a thermal deformation.
In the above structure, one notch hole may be formed so as to positioned above the light-source bulb. This allows the heat generated in the inner space of the reflector to be more efficiently dissipated into the outer space through that notch hole.
In the above structure, screwing portions for screwing the bulb fixing member to the annular wall may be formed at a plurality of circumferential positions in the rear end face of the annular wall. When the reflector has such screwing portions, it is preferable that each of the notch holes be provided ahead of each screwing portion; and this structure provides several advantages as described below.
The screwing portions of the annular wall must be formed with a boss-like shape; and this requires the annular wall to have a large thickness. If such thick screwing portions of the annular wall are formed so as extend to the reflector body, then the reflecting surface of the reflector formed as a resin molded member would have a large shrinkage cavity; and this would adversely affect the light distribution capability of the lamp fixture.
However, in the present invention, the notch holes are respectively provided in front of the screwing portions; and thus, the thick screwing portions of the annular wall do not extend to the reflector body. Accordingly, a large shrinkage cavity is prevented in the reflecting surface of the reflector.
In a lamp fixture that has a reflector housed in a lamp body, the lamp body often has an opening near the rear end of the reflector, which is larger than the outer diameter of the annular wall, and a cover member is often attached to the lamp body so as to close the opening.
In such a lamp fixture, a cover member provided with a reflector fitting hole that has a diameter approximately equal to the outer diameter of the annular wall is used, so that the reflector fitting hole is fitted on the outer peripheral surface of the annular wall of the reflector at a position behind the notch holes. With this structure, the cover member can seal the notch holes from the outer space of the lamp body, thus assuring waterproof and dustproof properties of the lamp fixture unit. In addition, the light-source bulb can be replaced without detaching the cover member from the lamp body.